Distributed digital cross-connect system and method

ABSTRACT

A distributed digital cross-connect system ( 10 ) is provided. The system includes two or more network interface islands ( 12 ) that connect to the telecommunications network. The system ( 10 ) also includes one or more distributed services nodes ( 18 ). Each distributed services node ( 18 ) connects to two or more of the network interface islands ( 12 ). The network interface islands ( 12 ) can transmit data to each other through the distributed services node ( 18 ). An administration system ( 14 ) is also connected to each distributed services node ( 18 ) and each network interface island ( 12 ). The administration system ( 14 ) transmits matrix configuration and telecommunications channel routing data to the network interface islands ( 12 ) and the distributed services nodes ( 18 ).

TECHNICAL FIELD OF THE INVENTION

This invention relates in general to the field of telecommunicationsystems, and more particularly to a distributed digital cross-connectsystem and method.

BACKGROUND OF THE INVENTION

Telecommunication systems are operable to connect two or moretelecommunications ports through a variety of data transmission media.For example, a first telecommunications port may be coupled to amicrowave data transmission medium, which may in turn be coupled to acopper conductor data transmission medium, then to a fiber optic datatransmission medium, and subsequently to a second telecommunicationsport. In this example, telecommunications data is transmitted through atelecommunications channel between the first telecommunications port andthe second telecommunications port via the microwave data transmissionmedium, the copper conductor data transmission medium, and the fiberoptic data transmission medium.

Modern telecommunication systems are typically comprised of a largenumber of telecommunications ports connected to a large number of datatransmission media. These media may utilize large signal frequencybandwidths, such that two or more telecommunications channels may becombined for transmission over the data transmission media bymultiplexing. In order to connect any given port to any other givenport, it is necessary to utilize specialized telecommunication switches,which are used to connect the data transmission media. Suchtelecommunication switches are capable of connecting any of a largenumber (M) of input ports to any of a large number (N) of output ports,with a different data transmission medium connected to each input andoutput port. Furthermore, these switches may be capable ofdemultiplexing the signal carried over a given media in order to provideswitching capability for multiplexed telecommunications channels.

A digital cross-connect system is a specialized telecommunicationsswitch that provides improved flexibility in switching services. Anexample of a modern digital cross-connect system is provided by U.S.Pat. No. 5,436,890 to Read et al entitled “Integrated Multi-rateCross-Connect System,” assigned to DSC Communications Corporation,issued Jul. 25, 1995 (hereinafter “Read”). In addition to atelecommunications switch operable to connect any of M input ports toany of N output ports, the digital cross-connect system taught in Readcontains redundant parallel planes of all components, such that thedigital cross-connect system can experience a number of failures in thecomponents that comprise both planes without loss of network traffic.

Despite the additional flexibility inherent in digital cross-connectsystems, connection of data transmission media to the digitalcross-connect system input ports and output ports must be coordinated inorder to optimize telecommunications traffic flow. For example, it maybe desirable to transmit telecommunications traffic from an input portof a first digital cross-connect system to an output port of a seconddigital cross-connect system. While this connection may be accomplishedby providing connections between an output port of the first digitalcross-connect system and an input port of the second digitalcross-connect system, such connections consume digital cross-connectsystem resources, i.e., input ports and output ports.

Furthermore, if two or more separate and discrete digital cross-connectsystems are being used to route telecommunications traffic, asignificant amount of digital cross-connect system resources must beused to interconnect the digital cross-connect systems. In many cases,it is desirable to use two or more physically separated digital crossconnects, such as when a small number of telephony circuits areconnected to network interfaces, but to later increase the number ofdigital cross connects and, subsequently, the number of connectionsbetween digital cross connects, such as when the number of telephonycircuits connected to network interfaces has increased. Presentlyavailable digital cross connect systems do not readily accommodate suchincreases in the number of network interfaces, and require networkinterfaces to be remapped in order to decrease the number of connectionswhich must be made between digital cross connect systems.

SUMMARY OF THE INVENTION

Therefore a need has arisen for a system and method for connecting adigital cross-connect system to network interfaces that readilyaccommodates increases in the number of network interfaces.

Accordingly, the present invention provides a system and method forconnecting a digital cross-connect system to network interfaces thatuses network interface islands, and which allows data communications tobe transmitted from an input port of any network interface island to anoutput port of any network interface island.

One aspect of th e present invention is a distributed digitalcross-connect system. The system includes two or more network interfaceislands that interface with the telecommunications system. The systemalso includes one or more distributed services nodes. Each distributedservices node connects to two or more network interface islands. Thenetwork interface islands transmit data to each other through thedistributed services node. An administration system is also connected toeach distributed services node and each network interface island. Theadministration system transmits switch configuration andtelecommunications channel routing data to the network interface islandsand the distributed services nodes.

The present invention provides several technical advantages. Oneimportant technical advantage of the present invention is that two ormore discrete network interface islands may be interconnected to adistributed services node that allows any input port of a networkinterface island to be switched to any output port of a networkinterface island.

Another important technical advantage of the present invention is thatthe number of network interface islands may be increased or decreasedwithout affecting the input and output port configurations of eachnetwork interface island.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and theadvantages thereof, reference is now made to the following descriptiontaken in conjunction with the accompanying drawings in which likereference numbers indicate like features and wherein:

FIG. 1 is a block diagram of an exemplary system architecture of adistributed digital cross-connect system embodying concepts of thepresent invention;

FIG. 2 is a block diagram of an exemplary unit shelf controlconfiguration showing the internal configuration of the networkinterface island components that control the connection of the networkinterface island to the master interface island and the distributedservices nodes;

FIG. 3 is an exemplary schematic diagram embodying concepts of thepresent invention and showing the data transmission path from digroupcircuits of the network interface island to the unit controller and tothe digital matrix interface;

FIG. 4 is an exemplary block diagram of the counter-rotating ringinterfaces that are used to receive switching and control data from thecontrol system communications media at each network interface island andto transmit switching and controls data to the control systemcommunications media from the master network interface island;

FIG. 5 is an exemplary schematic diagram showing the redundant planes ofthe control structure of the administration subsystem and the masternetwork interface island;

FIG. 6 is an exemplary schematic diagram of a timing hierarchy embodyingconcepts of the present invention;

FIG. 7 is an exemplary schematic diagram of a timing distribution systemembodying concepts of the present invention;

FIGS. 8A through 8D are exemplary data formats embodying concepts of thepresent invention;

FIG. 9 is a flow chart of an exemplary method for transmission of datafrom a first network interface island to a second network interfaceisland through a distributed services node;

FIG. 10 is an exemplary flow chart of a timing method for a distributeddigital cross-connect system; and

FIG. 11 is an exemplary method for transmitting digitally-encoded datain accordance with the teachings of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention are illustrated in theFIGURES, like numerals being used to refer to like and correspondingparts of the various drawings.

FIG. 1 is a block diagram of an exemplary system architecture of adistributed digital cross-connect system 10 embodying concepts of thepresent invention. As shown in FIG. 1, distributed digital cross-connectsystem 10 includes four network interface islands 11, 12, 15, and 17, amaster network interface island 13, an administration subsystem 14, asynchronization subsystem (SYNC) 16, and two distributed services nodes(DSN) 18. Distributed digital cross-connect system 10 also containsprovisions for an optional administration subsystem 20. Networkinterface islands 11, 12, 15, and 17, master network interface island13, and distributed services nodes 18 are coupled to control systemcommunications media 22. In addition, each network interface island 11,12, 15, and 17 and master network interface island 13 is coupled to eachdistributed services node 18 by data and timing media 24.Synchronization subsystem 16 is coupled to distributed services nodes 18by timing signal media 26.

Network interface islands 11, 12, 15, and 17 and master networkinterface island 13 comprise M input ports and N output ports, where “M”and “N” may be any suitable numbers. For example, a first networkinterface island 11 may provide distributed digital cross-connect system10 with 1096 input ports and 1096 output ports, and a second networkinterface island 15 may provide digital cross-connect system 10 with 548input ports and 548 output ports. These network interface islands areused to provide telecommunications network interfaces ports throughwhich telecommunications data transmission channels may be established.

For example, copper conductor data transmission media carrying DS1 levelsignals may be coupled to the input ports and the output ports ofnetwork interface islands 11, 12, 13, 15, and 17. A telecommunicationsdata transmission channel may need to be established between a firsttelecommunications port coupled to a first data transmission medium thatis coupled to an input port of a first network interface island, such asnetwork interface island 11, and a second telecommunications portcoupled to a second data transmission medium that is coupled to anoutput port of a second network interface island, such as networkinterface island 15. The present invention allows thistelecommunications data transmission channel to be established throughthe distributed services nodes 18 without connecting an output port ofnetwork interface island 11 to an input port of network interface island15.

As shown in FIG. 1, four network interface islands 11, 12, 15, and 17and master network interface island 13 are coupled to distributedservices nodes 18. Many suitable numbers of network interface islandsmay be connected to distributed services nodes 18. In addition, as shownin FIG. 1, each network interface island may comprise two redundantplanes. The use of two redundant planes is similar to the system andmethod shown in Read. Master network interface island 13 may beidentical to network interface islands 11, 12, 15, and 17, and may bethe only network interface island coupled directly to administrationsubsystem 14.

Administration subsystem 14 of distributed digital cross-connect system10 performs telecommunications routing and database maintenance fordistributed digital cross-connect system 10. As previously noted,administration subsystem 14 may be associated with master networkinterface island 13, such that communication with network interfaceislands 11, 12, 15, and 17 via control system communications media 22may require the intermediate step of transmitting the data to masternetwork interface island 13. Administration subsystem 14 may also bedistributed such that redundant administration subsystems 14 couple toone or more network interface islands 11, 12, 15, and 17, or may be in acentralized location and directly coupled to each network interfaceisland 11, 12, 15, and 17.

The network connections for each network interface island 11, 12, 15,and 17 are transmitted to administration subsystem 14 over controlsystem communications media 22. Likewise, connections establishedbetween input ports of each network interface island 11, 12, 13, 15, and17 and output ports of other network interface islands 11, 12, 13, 15,and 17 through distributed services node 18 are coordinated byadministration subsystem 14. Administration subsystem 14 furtherperforms database maintenance and telecommunications data transmissionchannel routing functions for distributed digital cross-connect system10.

Synchronization subsystem 16 is a timing subsystem for coordinatingcomponents of distributed digital cross-connect system 10.Synchronization subsystem 16 may be associated with master networkinterface island 13, in a manner similar to administration subsystem 14.Alternately, synchronization subsystem 16 may be centrally located andcouple directly to each subsystem and network interface island indistributed digital cross-connect system 10. Synchronization subsystem16 is a master timing system that receives network reference timingsignals from the network of data transmission media to which it isconnected (not explicitly shown). These timing signals are transmittedto the distributed services nodes timing systems (not explicitly shown)associated with distributed services nodes 18. Timing signals are thentransmitted to the timing systems of network interface islands 11, 12,15, and 17 and master network interface island 13 via data and timingmedia 24.

Distributed services nodes 18 are telecommunications switches having Minput nodes and N output nodes, and form a telecommunications datatransmission path between network interface islands 11, 12, 15, and 17and master network interface island 13. Distributed services nodes 18may include data processing equipment for converting optical signals toelectrical signals and for multiplexing and demultiplexing data, anddata processing equipment for converting between parallel and serialdata formats.

Control system communications media 22, data and timing media 24, andtiming signal media 26 are digital data transmission media, such ascopper conductors, coaxial conductors, optical conductors, or many othersuitable conductors. In the preferred embodiment, control systemcommunications media 22, data and timing media 24, and timing signalmedia 26 are optical conductors to obtain the highest data transmissionspeed. Digitally encoded telecommunications data is transmitted overthese media in various data formats.

In operation, data transmission media carrying dedicatedtelecommunications channels are coupled to network interface islands 11,12, 15, and 17 and master network interface island 13. For example, eachnetwork interface island 11, 12, 15, and 17 and master network interfaceisland 13 may comprise 1,024 incoming local telecommunications datachannels and 1,024 outgoing local telecommunications data channels. Eachnetwork interface island 11, 12, 15, and 17 and master network interfaceisland 13 can connect any of the 1,024 incoming local telecommunicationsdata channels to any of the 1,024 outgoing local telecommunications datachannels through distributed services nodes 18. These telecommunicationsdata channels may be conducted through a single data transmissionmedium, such as a fiber optic cable, or through multiple datatransmission media, such as individual copper conductors.

The connections between network interface islands 11, 12, 15, 17, andmaster network interface island 13 are formed through distributedservices nodes 18. For example, data and timing media 24 may eachconduct 1,024 telecommunications data channels between network interfaceislands 11, 12, 15, 17, and master network interface island 13 throughdistributed services nodes 18. These telecommunications data channelscarry telecommunications data from network interface islands 11, 12, 15,and 17 and master network interface island 13 to distributed servicesnodes 18, and also carry telecommunications data from distributedservices nodes 18 to network interface islands 11, 12, 15, and 17 andmaster network interface islands 13.

To further illustrate, a telecommunications data channel may need to beestablished between an input port of network interface island 11 and anoutput port of network interface island 15. The present invention allowsthat telecommunications data channel to be established from networkinterface island 11, through distributed services nodes 18, and tonetwork interface island 15.

In order to transfer digitally-encoded telecommunications data betweennetwork interface islands 11 and 15 and distributed services nodes 18,the timing of each distributed system must be traceable to a singlecommon frequency reference. The common frequency reference for eachnetwork interface island 11, 12, 15, and 17, master network interfaceisland 13, and distributed services nodes 18 is provided bysynchronization subsystem 16. Master network interface island 13 ischaracterized by being directly coupled to synchronization subsystem 16.All other network interface islands are coupled to synchronizationsubsystem 16 through master network interface island 13.

The routing of telecommunications traffic is coordinated byadministration subsystem 14. Thus, if telecommunications traffic must berouted from an input port of a first network interface island 11 to anoutput port of a second network interface island 15, routing signalsreceived by administration subsystem 14 are first converted to controlsignals that may include switching commands. Next, these control signalsare transmitted over control system communications media 22 fromadministration subsystem 14 to network interface islands 11 and 15involved in the data transmission path, and to distributed servicesnodes 18.

In response to these control signals, network interface islands 11 and15 and distributed services nodes 18 that form the data transmissionchannel path from the input port of the first network interface island11 to the output port of the second network interface island 15 areswitched to carry the telecommunications data channel. Switching issynchronized by synchronization subsystem 16 via timing signalstransmitted over timing signal media 26 and data and timing media 24.

One of ordinary skill in the art will recognize that various changes,substitutions, and alterations can be made to distributed digitalcross-connect system 10 without departing from the spirit or scope ofthe present invention. For example, many suitable numbers of networkinterface islands may be used, and that the present invention is notlimited to the four network interface islands and one master networkinterface island shown in FIG. 1. Likewise, many suitable datacommunications media may be used to transmit telecommunications data andadministration and control data between each of the network interfaceislands, the master access island, and the distributed services nodes.

FIG. 2 is a block diagram of an exemplary unit shelf controlconfiguration 30 showing the internal configuration of the networkinterface island components that control the connection of the networkinterface ports of network interface islands 11, 12, 15, and 17 and ofmaster network interface island 13 to distributed services nodes 18(FIG. 1). These connections are formed from digroup circuits (DC) 34 tounit controllers (UC) 36, which are contained within network interfaceislands 11, 12, 15, and 17 and master network interface island 13, andare controlled by digital matrix controllers (DMCs) 40 of access shelves38. Unit shelf control configuration 30 as shown includes the accessshelves for network interface islands 11, 12, 15, and 17.

Unit shelf control configuration 30 for each network interface islandcontains 48 DS1 unit shelves 32 and two redundant digital matrixcontrollers 40. DS1 unit shelf 32 may be a discrete telecommunicationssystem component that includes a number of digroup circuits 34 and unitcontrollers 36. For example, DS1 unit shelf 32 may be a printed circuitboard card that includes discrete circuit components. DS1 unit shelf 32is comprised of, for example, 28 individual digroup circuits 34 and tworedundant unit controllers 36. Alternately, DS1 unit shelf 32 may becomprised of more than one discrete telecommunications system component,such as two printed circuit boards and a parallel data communicationsmedia connector, and many suitable numbers of digroup circuits 34 andunit controllers 36.

Forty-eight DS1 unit shelves 32 couple to digital matrix controller 40of access shelf 38. Each DS1 unit shelf 32 receives a number of serialtelecommunications data streams at a first frequency at digroup circuits34 from a network interface island. These serial data streams areconverted into a parallel data stream at a second frequency by unitcontroller 36. Control data received from digital matrix controller 40is embedded into the parallel data streams.

Digroup circuit 34 may be a discrete telecommunications switchcomponent, such as an integrated circuit within a single integratedcircuit package, that receives a single digitally encoded serial datastream or channel from an external telecommunications data transmissionmedium. Alternately, digroup circuit 34 may be comprised of more thanone discrete circuit component, or may be included in a single discretenetwork interface island component with one or more other digroupcircuits 34. For example, digroup circuit 34 may include two or moreintegrated circuit packages, discrete components, and associatedconductors.

Unit controller 36 in DS1 unit shelf 32 may be a discretetelecommunications component, such as a printed circuit card, aseparately-packaged integrated circuit, or similar discrete component.Alternately, unit controller 36 may be comprised of one or more discretetelecommunications components. Unit controller 36 receives a pluralityof discrete serial telecommunications data channels carrying digitallyencoded serial data in a first data format at a first frequency,converts the first data format to a second data format at a secondfrequency, and includes control data received from digital matrixcontroller 40 into the second data format.

For example, digroup circuit 34 may receive a first serial data formatof 8 bit words at a rate of 1.536 megabits per second, and may convertthis data to a second data format of 21-bit words at a rate of 4.032megabits per second. Control data received from digital matrixcontroller 40 is included in the additional 13 bits of data in each wordby unit controller 36. Unit controller 36 may also convert the seconddata format of serial data into a third data format of parallel data.For example, unit controller 36 may convert the 21-bit words of serialdata from the 28 digroup circuits 34 into 16-bit words of parallel data.This parallel data is transmitted to access shelf 38 at a rate of 5.376million words per second for subsequent transmission to distributedservices nodes 18.

In addition to digital matrix controller 40, access shelf 38 may includealarm units, power supplies, and other suitable components. Digitalmatrix controller 40 receives switching and control data fromadministration system 14 via control system communications media 22 anddigroup circuit 34 inserts this switching and control data into the datastream being transmitted from digroup circuit 34 to unit controller 36.

FIG. 3 is an exemplary schematic diagram 44 embodying concepts of thepresent invention and showing the data transmission path from digroupcircuits 34 to unit controllers 36 and to a digital matrix interface 46.This data transmission path is also contained within access shelves 38(FIG. 2) of network interface islands 11, 12, 15, and 17 and masternetwork interface island 13 (FIG. 1). Each digroup circuit 34 receives aDS1 serial telecommunications data signal comprised of 8-bit words froman external telecommunications data transmission media. The 28 digroupcircuits 34 are coupled to one unit controller 36, which converts the 288-bit serial telecommunications data signals into a single 16-bitparallel data signal for transmission to digital matrix interface 46.Eight digital matrix interfaces 46 are contained within one access shelf38 of FIG. 3.

Digital matrix interface 46 is a telecommunications switching componentthat receives the 16-bit parallel data signals from unit controllers 36and multiplexes these signals into a single signal carrying digitallyencoded data. Digital matrix interface 46 includes a multiplexer 48which is coupled to a 16-to-10 bit converter 50. 16-to-10 bit converter50 is coupled to electrical/optical converter 52. As shown in FIG. 3,six 16-bit parallel data signals from unit controllers 36 are receivedat multiplexer 48, and are multiplexed into a single 16-bit paralleldata signal that is transmitted to 16-to-10 bit converter 50. 16-to-10bit converter 50 converts the 16-bit parallel data signal received bymultiplexer 48 into a 10-bit parallel data signal. This 10-bit paralleldata signal and other 10-bit parallel data signals from a slave digitalmatrix interface 46 is then converted from an electrical to an opticalsignal by electrical/optical converter 52 and is transmitted todistributed services nodes 18.

After the optical data signal is received at distributed services nodes18, it is separated into individual data channels corresponding to theoriginal DS0 or DS1 data signals in a process that is partially thereverse of the process shown in FIG. 3. The optical data signal is firstconverted back to two 10-bit parallel electrical data signals by anoptical to electrical converter (not explicitly shown). The 10-bitparallel data signals (32,256 10-bit parallel data signals) for theeight digital matrix interfaces 46 for each access shelf 38 are thenswitched through the switching matrix of the distributed services nodes18, in addition to the 10-bit parallel data signals received from othernetwork interface islands 11, 12, 13, 15, and 17. In the preferredembodiment, up to 5,376 DS1 signals (129,024 DS0 signals) can beswitched by the switching matrix of each distributed services node 18,although any suitable number of matrix input ports and output ports maybe used.

At the output port side of the switching matrix in distributed servicesnodes 18, two 10-bit parallel data signals are converted to an opticalsignal for transmission to network interface islands 11, 12, 13, 15, and17. The optical signal is then converted back into serial DS1 datastreams, which subsequently transmitted over external data transmissionmedia.

One of ordinary skill in the art will recognize that various changes,substitutions, and modifications may be made to the system of FIG. 3without departing from the spirit or scope of the present invention. Forexample, many suitable numbers of DS1 signals may be converted fromserial to parallel data, and the size of parallel data words may bevaried from those stated, where suitable for a given purpose. Inaddition, the step of converting from an electrical signal to an opticalsignal may be omitted, if electrical signals are transmitted over dataand timing media 24. Additional error monitoring and alarm equipment,data processing equipment, and data transmission equipment may be addedto the data transmission path where suitable. For example, a data buffermay be used to temporarily store data in the event of a timing error, toincrease the reliability of the system.

FIG. 4 is an exemplary block diagram 54 of the counter-rotating ringinterfaces that are used to receive switching and control data fromcontrol system communications media 22 at each network interface island11, 12, 15, and 17, and to transmit switching and controls data tocontrol system communications media 22 from master network interfaceisland 13. Block diagram 54 includes redundant “A” and “B” plane digitalmatrix controllers 40 for each network interface island 11, 12, 15, and17 and master network interface island 13 that are coupled to clockwisering “A” 58, counter clockwise ring “A” 60, clockwise ring “B” 62, andcounter clockwise ring “B” 64, which comprise control systemcommunications media 22. Distributed services nodes 18 are also coupledto clockwise ring “A” 58, counter clockwise ring “A” 60, clockwise ring“B” 62, and counter clockwise ring “B” 64.

Digital matrix controller 40 receives control and switching commandsfrom clockwise ring “A” 58, counter clockwise ring “A” 60, clockwisering “B” 62, and counter clockwise ring “B” 64 at the counter-rotatingring interface shown in block diagram 54. Each network interface island11, 12, 15, and 17 and master network interface island 13 contains adigital matrix controller 40, and a corresponding counter-rotating ringinterface. In addition, connections between administration subsystem 14and clockwise ring “A” 58, counter clockwise ring “A” 60, clockwise ring“B” 62, and counter clockwise ring “B” 64 are made through the digitalmatrix controller 40 of master network interface island 13. Aspreviously noted, each network interface island of network interfaceislands 11, 12, 15, and 17 and master network interface island 13contains parallel planes of redundant components. In this regard, the“A” rings couple to the “A” plane of each network interface island, andthe “B” rings couple to the “B” plane of each network interface island.

In operation, control and switching commands determined byadministration subsystem 14 are transmitted on the counter-rotating ringinterface of master network interface island 13 to clockwise ring “A”58, counter clockwise ring “A” 60, clockwise ring “B” 62, and counterclockwise ring “B” 64. Control and switching commands are thentransmitted to each network interface island 11, 12, 15, and 17 throughthe counter-rotating ring interface of each network interface island. Itshould be noted that control and switching commands for each parallelplane of the network interface island of network interface islands 11,12, 15, and 17 are transmitted over two redundant paths.

For example, for plane A of network interface islands 11, 12, 15, and17, master network interface island 13, and distributed services nodes18, switching and control commands are transmitted over clockwise ring“A” 58 and counter clockwise ring “A” 60. Likewise, for plane B ofnetwork interface islands 11, 12, 15, and 17, master network interfaceisland 13, and distributed services nodes 18, switching and controlcommands are transmitted over clockwise ring “B” 62 and counterclockwise ring “B” 64. This configuration ensures that a path betweeneach network interface island 11, 12, 15, and 17 will be availablefollowing a construction accident or similar break at one point alongclockwise ring “A” 58, counter clockwise ring “A” 60, clockwise ring “B”62 or counter clockwise ring “B” 64.

One of ordinary skill in the art will recognize that various changes,substitutions, and alterations can be made to the counter-rotating ringinterface shown in FIG. 4 without departing from the spirit or scope ofthe present invention. For example, a single set of counter-rotatingrings may be utilized, or the master network interface island may coupledirectly to the counter-rotating rings, if suitable.

FIG. 5 is an exemplary schematic diagram showing the redundant planes ofcontrol structure 70 of administration subsystem 14 and master networkinterface island 13. Control structure 70 includes digital matrixcontrollers (DMC) 40 for the A plane and B plane of the master networkinterface island 13, which are coupled to the digital matrix interfaces(DMI) 46 of master network interface island 13. The digital matrixcontrollers 40 are also connected to clockwise ring “A” 58, counterclockwise ring “A” 60, clockwise ring “B” 62 or counter clockwise ring“B” 64, to form the counter-rotating ring interface for master networkinterface island 13. Plane “A” of control D structure 70 couples to asingle alarm interface (AI) 72. Both planes couple to a memory storageunit 74. Synchronization circuit cards (SYNC) 76 are coupled to digitalmatrix controllers 40.

Alarm interface 72 is a telecommunications system administration systemcomponent that is coupled to microprocessor 78 and unit manager 80 ofthe “A” plane. Alarm interface 72 receives alarm notifications frommicroprocessor 78 or unit manager 80 that may be derived from overheadswitching and control data, and transmits these alarm notifications toan alarm monitor (not explicitly shown) or other suitable component tonotify operators of equipment failure, power supply failures, or othermalfunctions.

Memory storage 74 is a digital data memory storage device for storingcontrol and switch configuration information. For example, memorystorage unit 74 may contain data that describes the currentconfiguration of each network interface island 11, 12, 15, and 17 andmaster network interface island 13. Memory storage unit 74 may be amagnetic diskette or tape data storage device, a random access memory(RAM), an optical digital data storage device, or other suitable digitaldata memory devices.

Synchronization circuit card 76 receives timing signals from externaltiming sources, processes these timing signals, and transmits timingsignal status related information to the digital matrix controller 40.The timing signals received and processed by synchronization circuitcard are transmitted to the timing system of distributed services nodes18 and the timing systems of network interface islands 11, 12, 15, and17 and master network interface island 13. These transmitted timingsignals are used to coordinate the transmission of pulse code modulateddata between the distributed service nodes 18 network interface islands11, 12, 13, 15, and 17.

In operation, telecommunications routing commands are received atmicroprocessor 78 from an external source (not explicitly shown). Thesetelecommunications routing commands are processed by microprocessor 78,which uses data stored in memory storage 74 that includes the currentdigital cross-connect system matrix configuration for distributedservices nodes 18 and the network connections for each network interfaceisland 11, 12, 15, and 17 and master network interface island 13 todetermine the matrix connections that are necessary to form thetelecommunications data transmission path required by thetelecommunications routing commands. This telecommunications datatransmission path may include connections between network interfaceislands 11, 12, 15, and 17 and master network interface island 13through distributed services nodes 18.

Microprocessor 78 then transmits this matrix connection data to unitmanager 80, which converts the data to switching component commands andaddresses. These switching component commands and addresses are thentransmitted to digital matrix controllers 40, which process the commandsfor network interface islands 11, 12, 15, and 17 and master networkinterface island 13. Command status (is then returned to microprocessor78.

If the processed commands are addressed to the digital matrix interfaces46 of master network interface island 13, digital matrix controllers 40of master network interface island 13 route the processed commands tothe appropriate digital matrix interfaces 46. Otherwise, the processedcommands are transmitted from digital matrix controllers 40 of masternetwork interface island 13 to the digital matrix controllers 40 ofnetwork interface islands 11, 12, 15, and 17 via clockwise ring “A” 58,counter clockwise ring “A” 60, clockwise ring “B” 62 and counterclockwise ring “B” 64.

One of ordinary skill in the art will recognize that various changes,substitutions, and alterations can be made to the administration systemshown in FIG. 5 without departing from the spirit or scope of thepresent invention. For example, administration system 14 may bedistributed, such that a redundant administration system 14 is presentat each network interface island. Alarm interfaces and other componentsmay be omitted or relocated, if suitable. Likewise, additional dataprocessing equipment and data transmission system components may beadded without departing from the spirit and scope of the presentinvention.

FIG. 6 is an exemplary schematic diagram of a timing hierarchy 90embodying concepts of the present invention. Timing hierarchy 90includes master timing system 92 a and redundant master timing system 92b, which are coupled to main timing systems 94 a and 96 a, and backuptiming system 94 b and 96 b of distributed services nodes 18. Primarynetwork reference 98 and secondary network reference 99 couple to mastertiming island 92. The distributed services nodes timing systems arecoupled to the timing systems of the redundant planes of networkinterface islands 11, 12, and 15 and master network interface island 13.

In operation, timing signals derived from primary network reference 98and secondary network reference 99 are received by a synchronizationcard (not explicitly shown) of master timing systems 92 a and 92 b.These network reference timing signals are used to generate a referencesignal for master timing systems 92 a and 92 b that is insynchronization with the network reference timing signals. The referencetiming signals from master network interface island timing systems 92 aand 92 b are then transmitted to the distributed services nodes maintiming systems 94 a and 96 a, and distributed services nodes backuptiming systems 94 b and 96 b.

The distributed services nodes main and backup timing systems of bothplanes generate reference timing signals that are in synchronizationwith and in phase with the timing reference signal received from themaster network interface island timing systems 92 a or 92 b. Thedistributed services nodes timing reference signals are also exchangedbetween the redundant planes. If there is a conflict between any ofthese timing signals, an alarm signal may be generated, and theerroneous timing signal may be isolated and ignored. The distributedservices node timing signals are then embedded in data framestransmitted from distributed services nodes 18 to network interfaceislands 11, 12, and 15 and master network interface island 13. Localtiming reference signals are generated at each network interface island11, 12, and 15 and at master network interface island 13, and aresynchronized and phase-aligned to one of the timing signals embedded inthe transmitted data frames.

One of ordinary skill in the art will recognize that various changes,substitutions, and alterations can be made to the timing hierarchy shownin FIG. 6 without departing from the spirit or scope of the presentinvention. For example, timing signals may be transmitted directly fromthe master network interface island to all network interface islands, ifsuitable.

FIG. 7 is an exemplary schematic diagram of a timing distribution system100 embodying concepts of the present invention. Timing distributionsystem 100 includes a master timing system 102, which is coupled todistributed services node timing systems 104 and 106, which couple to anexemplary network interface island timing system 108 that is containedwithin an network interface island, such as network interface island 11,12, 15, or 17, or master network interface island 13.

Master timing system 102 performs functions similar to synchronizationsubsystem 16 of FIG. 1. Master timing system 102 includes independenttiming generators (SYNC) 110 and 112, which are coupled to opticalsynchronization distributors 114 and 116. Independent timing generators110 and 112 are also coupled to network timing references 98 and 99,which transmit timing reference signals present on thetelecommunications network.

Distributed services nodes timing systems 104 and 106 are two redundantplanes of components that perform timing functions for distributedservices nodes 18. As previously mentioned, distributed services nodes18 and other components of distributed digital cross-connect system 10comprise two redundant planes of components, such that distributeddigital cross-connect system 10 may remain operable after the failure ofone or more components. Distributed services nodes timing systems 104and 106 include primary timing generators (TGEN) 118 and 122,respectively, and backup timing generators (TGEN) 120 and 124,respectively. Each primary timing generator 118 and 122 and backuptiming generator 120 and 124 are coupled to optical synchronizationdistributors 114 and 116, respectively, via optical conductors 134.Primary timing generator 118 and 122 and backup timing generator 120 and124 are also coupled to phase locked loops 126, which couple toelectrical to optical converters 128.

Electrical to optical converters 128 of distributed services nodestiming systems 104 and 106 may be coupled to digital matrix interfaces130 and 132 of exemplary network interface island timing system 108 byoptical conductors 138 and 140. Digital matrix interfaces 130 and 132 ofexemplary network interface island timing system 108 couple to timinggenerators 133, which cross-connect to each other.

Primary timing generators 118 and 122 of distributed services nodestiming systems 104 and 106 are used to provide a reference timing signalfor transmission to exemplary network interface island timing system108. Backup timing generators 120 and 124 are used only in the event offailure of primary timing generators 118 and 122, but may alternately beused in other situations where suitable. The distributed services nodereference timing signal is embedded into the data as it is transmittedto exemplary network interface island timing system 108 from distributedservices nodes timing systems 104 and 106.

Exemplary network interface island timing system 108 includes digitalmatrix interfaces 130 and 132 and timing generators 133, which arecoupled to electrical to optical converters 128. Digital matrixinterfaces 130 and 132 extract the timing reference signal embedded inthe data frame by distributed services nodes timing systems 104 and 106,and provide the extracted timing signal to the timing generators 133.

In operation, network timing references are received at independenttiming generators 110 and 112 of master timing system 102. Independenttiming generators 110 and 112 generate a timing signal that may besynchronized and in phase with network timing references 98 and 99.Independent timing generators 110 and 112 transmit the timing signal tooptical synchronization distributors 114 and 116, which in turn transmitthe timing signal via optical conductors 134 to primary timinggenerators 118 and 122 and backup timing generators 120 and 124 ofdistributed services nodes timing systems 104 and 106, respectively.This connection path is used to transmit the reference timing signal ofmaster timing system 102 to distributed services nodes timing systems104 and 106.

The reference timing signal is then transmitted to network interfaceisland timing system 108 by embedding a timing signal in the data thatis transmitted from distributed services nodes 18 to network interfaceislands 11, 12, 15, and 17 and master network interface island 13.

Timing generators 118, 120, 122, and 124 are high accuracy timinggenerators operating at either 64.512 MHZ or 32.256 MHZ. Timinggenerators 118, 120, 122, and 124 are operable to receive a networkreference clock signal of 64.512 MHZ and to generate local referenceclock signals of 32.256 MHZ and 8.064 MHZ. In addition, timinggenerators 118, 120, 122, and 124 are operable to perform otherconventional functions, such as activity testing of reference signals,extraction of timing signals from a data stream, buffering timingsignals, and synchronizing a local timing signal with a reference timingsignal.

One of ordinary skill in the art will recognize that various changes,substitutions, and alterations can be made to timing distribution system100 without departing from the spirit and scope of the presentinvention. For example, electrical conductors may be utilized instead ofoptical conductors and backup timing generators may be omitted, wheresuitable.

FIGS. 8A through 8C are exemplary data formats embodying concepts of thepresent invention. FIG. 8A shows an exemplary conventional DS1 dataformat comprising one extended superframe 142, twenty four frames 144,and twenty four channels 146. Each channel 146 comprises eight bits ofdigitally encoded data. As shown in FIG. 8A, one channel has atransmission time of 5.2 microseconds, which corresponds to a datatransmission rate of 1.544 million bits per second.

FIG. 8B shows an exemplary data format 147 embodying concepts of thepresent invention. Data format 147 includes one extended superframe (notexplicitly shown), twenty four frames 148, and twenty four channels 150.Each channel comprises twenty one bits of digitally encoded data and hasa transmission time of 5.2 microseconds, which corresponds to a datatransmission rate of 4.032 million bits per second. As shown in FIG. 8B,in addition to the original eight bits of digitally encoded data fromchannel 146 of FIG. 8A, channel 150 of data format 147 includes a robbedbit signaling bit as bit 8, a frame bit as bit 9, a trunk conditioningindicator bit as bit 12, a path identity bit as bit 14, a parity bit asbit 15, and a control channel bit as bit 16. All other unassigned bitsmay carry random data values, or may be assigned to carry additionaldata when suitable.

FIG. 8C shows an exemplary data transmission flow chart 158 embodyingconcepts of the present invention. Data transmission flow chart 158shows the conversion steps taken to transmit data between a networkinterface island and a distributed services node. Data transmission flowchart 158 includes twenty eight parallel channels 152 of serial data,serial to parallel converter 154, and parallel data frame 156. Thetwenty eight parallel channels 152 of serial data are twenty eightchannels 150 as shown in FIG. 8B. Serial to parallel converter 154receives the twenty eight parallel channels 152 and truncates unassigneddata bits, as described in regards to FIG. 8B. For example, serial toparallel converter 154 may include data storage devices that store thetwenty eight parallel channels 152 of serial data as they are receivedand subsequently transmit the stored data as parallel data. Theremaining sixteen bits of digitally encoded data are transmitted oversixteen parallel conductors in parallel data frame 156.

FIG. 8D shows an exemplary 10-bit parallel data format 159 embodyingconcepts of the present invention. 10-bit parallel data format 159includes data from 24 frames of 16-bit parallel data frame 156. Inaddition to 8 bits of data, parallel data frame 156 includes five bitsof control, timing, and signaling data and three bits of unused data.This data is compressed from 16-bit parallel data frame 156 to 10-bitparallel data frame 159 by eliminating redundant data. For example, thetrunk conditioning indicator (TCI) may be sent once every six frames, asit is set after at least a one second filter for most errors, and thetransmission time of six frames is 750 microseconds. Likewise, channelID, parity, and other data may be compressed.

In operation, digitally-encoded, serially transmitted data is receivedat the network interface island in the data format shown in FIG. 8A,which is a conventional DS1 data format. This data includes eight bitsof telecommunications data. Data format 147 of the present inventionutilizes a higher data transmission rate to increase the amount of datathat can be transmitted in one 5.2 microsecond channel. In addition tothe eight bits of telecommunications data, channel 150 includes 13additional bits of data, including robbed bit signaling data, frame bitdata, trunk conditioning indicator data, path identification data,parity data, and control channel data. Twenty eight channels 152 ofserial data in data format 152 are converted to parallel data format156. This data is converted to 10 bit format 159 shown in FIG. 8D and istransmitted from an network interface island to the distributed servicesnode. The same format is used to transmit data from the distributedservices node to the network interface island.

The data formats shown in FIGS. 8A through 8D may have many suitablenumber of components. In general, the data format of FIG. 8A may have Qextended superframes of P frames of N channels of M-bit words, and thedata format of FIG. 8B may have Z extended superframes of Y frames of Xchannels of W-bit words, where M bits of the W-bit word are the datafrom the data format of FIG. 8A, and R bits of the W-bit word are otherdata, and where M, N, P, Q, R, W, X, Y, and Z are suitable integers thatsatisfy the above criteria. For example, the sum of M and R cannot begreater than W.

One of ordinary skill in the art will recognize that various changes,substitutions, and alterations can be made to the data format describedabove without departing from the spirit or scope of the presentinvention. For example, the unassigned data bits may be omitted, or maybe assigned other suitable data values. Likewise, the parallel datatransmission format may be modified to include more or less than sixteenbits, as shown in FIG. 8C.

FIG. 9 is a flow chart 160 of an exemplary method for transmission ofdata in a distributed digital cross-connect system from a first networkinterface island to a second network interface island through adistributed services node. The method begins at step 162, where routingcommands are received at the administration subsystem 14. These routingcommands may include a first network interface island input port and asecond network interface island output port, between which a datatransmission channel must be established. At step 164, administrationsubsystem 14 determines, from data that represent the current status ofall components of distributed digital cross-connect system 10, a datatransmission channel between the network interface islands 11, 12, 13,15, and 17 and distributed services nodes 18.

Administration subsystem 14 transmits control commands for establishingthe data transmission channel at step 166 between the network interfaceislands 11, 12, 13, 15, and 17 and the distributed services nodes 18.These connections are formed at step 168. At step 170, the serial datathat is to be transmitted over the data communications channel isreceived at the first network interface island input in a standard DS1format. This serial data is then multiplexed at step 172 to a higherserial data rate at the unit shelf of the network interface island. Thehigh-speed serial data is then converted to a parallel 16-bit dataformat such as 16-bit parallel data format 156 of FIG. 8C at step 174.

At step 176, the parallel 16-bit data is multiplexed to a second higherspeed, and is then converted to a 10-bit parallel format such as 10-bitparallel format 159 of FIG. 8D at step 178. At step 180, the 10-bitparallel data format is converted from an electrical to an opticalsignal for transmission from the network interface island to thedistributed services nodes at step 182.

At step 184, the optical signal is converted to an electrical signal atthe distributed services nodes. At step 186, the data is switchedthrough the switching matrix of the distributed services nodes, and issubsequently converted back to an optical signal at step 188. Thisoptical signal is then transmitted from the distributed services nodesto the network interface islands at step 190.

At step 192, the 10-bit parallel optical signal is converted to anelectrical signal at the network interface island, and is then convertedto a 16-bit parallel signal at step 194. At step 196, overhead data suchas control and switching data is provided to the unit shelf, which usesthe data to convert the 16-bit parallel signal to a serial signal atstep 198. This serial data is then transmitted to the network connectionof the appropriate digroup circuit at step 200.

One of ordinary skill in the art will recognize that various changes,substitutions, and alterations can be made to the method described abovewithout departing from the spirit or scope of the present invention. Forexample, the step of converting from electrical to optical may beomitted, if suitable. Likewise, the steps of multiplexing anddemultiplexing data signals may be omitted if suitable.

FIG. 10 is an exemplary flow chart 220 of a timing method fordistributed digital cross-connect system 10. The timing method begins atstep 222, where a network timing reference signal is received atindependent timing generators 110 and 112 of FIG. 7 which compriseredundant master timing systems 102. At step 224, a reference timingsignal is generated at each independent timing generator 110 and 112 ofmaster timing systems 102. These master timing system reference timingsignals are transmitted between the redundant planes of master timingsystem 102 at step 226 to optical synchronization distributors 114 and116. A common reference timing system timing reference signal is thenestablished between the redundant planes of master timing system 102,and is transmitted at step 228 from optical synchronization distributors114 to primary timing generators 118 and 122 and backup timinggenerators 120 and 124 of distributed services nodes timing systems 104and 106, respectively.

At step 230, the primary or backup timing generator is chosen based upona suitable selection criteria, such as whether primary timing generators118 and 122 are operable. At step 232, reference timing signals aretransmitted between distributed services nodes timing systems 104 and106 to allow the systems to be synchronized. At step 234, the referencetiming signals of distributed services nodes timing systems 104 and 106are embedded in a data frame that is to be transmitted from thedistributed services node 18 to one of network interface islands 11, 12,13, 15, and 17.

At step 238, network interface island timing system 108 derives areference timing signal from the embedded timing signal, and alsoreceives a local timing signal from a local oscillator. Networkinterface island timing system 108 then uses this reference timingsignal to align the phase of a locally generated timing signal at step240. In this manner, the timing of distributed digital cross-connectsystem 10 may be coordinated such that all components of distributeddigital cross-connect system 10 may obtain a synchronized timingreference signal.

One of ordinary skill in the art will recognize that various changes,substitutions, and alterations can be made to the method described abovewithout departing from the spirit or scope of the present invention. Forexample, the steps of embedding a reference signal in a data frame maybe omitted and replaced with steps of transmitting timing signals over adedicated timing channel.

FIG. 11 is an exemplary method 250 for transmitting digitally-encodeddata in accordance with the teachings of the present invention. At step252, first serial data is received at a first frequency. For example,the first serial data may comprise a standard DS1 channel with 8 bits ofdigitally-encoded data. This first serial data is stored at step 254,then retrieved and transmitted at a higher frequency at step 256. Afterthe first serial data has been transmitted, second serial data istransmitted at step 258. For example, this first and second serial datamay be transmitted in a data format such as channel 150 of FIG. 8B,where the first serial data may be bits 0 through 7 of frame 150, andthe second serial data may be bits 8 through 20 of frame 150.

The combined first and second serial data may then be received at aserial to parallel converter, such as serial to parallel converter 154,and the serial data words may then be truncated at step 260. Forexample, any unassigned bits may be truncated, as shown in FIG. 8C. Thistruncated serial data may then be stored and converted to parallel dataat step 262. The parallel data is then transmitted at step 264, such asbetween a network interface island of one of network interface islands11, 12, 13, 15, and 17 and distributed services node 18.

One of ordinary skill in the art will recognize that various changes,substitutions, and alterations can be made to the method described abovewithout departing from the spirit or scope of the present invention. Forexample, the step of truncating data at step 260 may be omitted if thereis no undesignated data in the serial data. Likewise, the step oftransmitting in parallel may be omitted, if suitable.

The present invention offers many technical advantages. One importanttechnical advantage of the present invention is that two or morediscrete network interface islands may be interconnected in a mannerthat allows any input port of the interconnected network interfaceislands to be switched to any output port of the interconnected networkinterface islands. Another important technical advantage of the presentinvention is that the number of interconnected network interface islandsmay be increased or decreased without affecting the input and outputport configurations of the network interface islands.

Although the present invention has been described in detail, it shouldbe understood that various changes, substitutions, and alterations canbe made hereto without departing from the spirit and scope of theinvention as defined by the appended claims.

What is claimed is:
 1. A method for connecting two or more networkinterface islands comprising the steps of: transmitting timing data to afirst network interface island, a second network interface island, and adistributed services node; transmitting controls data to a first networkinterface island, a second network interface island, and a distributedservices node; connecting the first network interface island to thesecond network interface island through the distributed services node;wherein the step of transmitting controls data comprises the steps of:receiving a routing request at an administration system for establishinga connection path from a first telecommunications address to a secondtelecommunications address; determining a connection path from a firstnetwork interface island input port to a second network interface islandoutput port through a first distributed services node that will form theconnection path from the first telecommunications address to the secondtelecommunications address; and transmitting control commands to thefirst network interface island, the second network interface island, andthe distributed services node; wherein the step of transmitting controlcommands comprises the steps of: transmitting control commands to thefirst network interface island, the second network interface island, andthe distributed services node over a first fiber optic conductor,wherein the first fiber optic conductor is coupled to the first networkinterface island, the second network interface island, and thedistributed services node in a first direction relative to each networkinterface island; and transmitting control commands to the first networkinterface island, the second network interface island, and thedistributed services node over a second fiber optic conductor, whereinthe second fiber optic conductor is coupled to the first networkinterface island, the second network interface island, and thedistributed services node in a second direction relative to each networkinterface island.
 2. The method of claim 1 wherein the step oftransmitting control commands further comprises the steps of:transmitting control commands to a first redundant plane of the firstnetwork interface island, a first redundant plane of the second networkinterface island, and a first redundant plane of the distributedservices node over a first fiber optic conductor, wherein the firstfiber optic conductor is coupled to the first redundant plane of thefirst network interface island, the first redundant plane of the secondnetwork interface island, and the first redundant plane of thedistributed services node in a first direction relative to each networkinterface island; transmitting control commands to the first redundantplane of the first network interface island, the first redundant planeof the second network interface island, and the first redundant plane ofthe distributed services node over a second fiber optic conductor,wherein the second fiber optic conductor is coupled to the firstredundant plane of the first network interface island, the firstredundant plane of the second network interface island, and the firstredundant plane of the distributed services node in a second directionrelative to each network interface island; transmitting control commandsto a second redundant plane of the first network interface island, asecond redundant plane of the second network interface island, and asecond redundant plane of the distributed services node over a thirdfiber optic conductor, wherein the third fiber optic conductor iscoupled to the second redundant plane of the first network interfaceisland, the second redundant plane of the second network interfaceisland, and the second redundant plane of the distributed services nodein a first direction relative to each network interface island; andtransmitting control commands to the second redundant plane of the firstnetwork interface island, the second redundant plane of the secondnetwork interface island, and the second redundant plane of thedistributed services node over a fourth fiber optic conductor, whereinthe fourth fiber optic conductor is coupled to the second redundantplane of the first network interface island, the second redundant planeof the second network interface island, and the second redundant planeof the distributed services node in a second direction relative to eachnetwork interface island.